Many agricultural processes require the delivery of a granular material, such as seed, fertilizer, and the like, from a bulk storage tank toward an outlet or secondary containment system. The granular material is often motivated pneumatically through a series of lines. The flow of granular material through the lines is typically classified as one of two general types, specifically, the granular material may be motivated in a dilute phase flow or in a dense phase flow. During dilute phase flow, the volume percentage of air in the line is much greater relative to the volume percentage of granular material. Alternatively, during dense phase flow the relative ratio is reversed, meaning that a greater volume percentage of granular material is motivated through the line by a lower volume percentage of air.
Dense phase flow provides various benefits. Overall, dense phase flow is more efficient as compared to dilute phase flow because more granular material can be transferred from one location to another with less energy. Moreover, dense phase flow can be generally operated with line velocities under four feet per second and motive pressures below approximately fourteen pounds per square inch gauge. This low velocity/pressure provides smooth, gentle transfer of the granular material through the line thereby reducing damage to the granular material. Also, since near full pressure resides in the lines at startup, starting the dense phase flow occurs quickly when desired. Further, dense phase flow allows for fewer, smaller lines to be used as compared to dilute phase flow (e.g., two 2″ diameter dense phase lines can be configured to transport substantially the same rate of granular material as eight 2.5″ lines using dilute phase flow). Dense phase flow also provides improved flexibility to deliver product sectionally without the need for bulky, costly, and repetitious equipment (e.g., sectional distribution using dilute phase flow may require multiple metering sections, independent air supplies to create the dilute phase flow, etc.).
Dense phase flow, however, presents a series of challenges, especially when used in the agricultural context. When dense phase flow is incorporated in the agricultural context, the overall dense phase distribution system is limited in capacity by practical considerations (i.e., the amount or volume of air that can be supplied to the system to deliver the granular material from a bulk storage tank to the ultimate application is limited by space, power, and other operating conditions).
The challenges are exacerbated by the inclusion of a branch in the system. A branch diverts the upstream flow of granular material into two or more downstream flows, thereby allowing the granular material to be distributed to multiple outlets or secondary containments (albeit not necessarily simultaneously as a downstream valve can control an end of the line outlet, and therefore conserve the available air). A branch typically results in an increased cross-sectional area and a decrease in the velocity (and momentum) of the granular material through a branch. This decrease in velocity is in addition to the resistance attributable to typical line flow losses and resistance resulting from relative movement between grains of the granular material. Limited pneumatic capacity prevents the “simple” solution of increasing the flow rate of air in the lines to counterbalance the expanded area of the branch. An increased pneumatic flow rate will also reduce some of the benefits of dense phase, such as the smooth, gentle flow of the granular material. As a result, the limited pneumatic capacity and typical branch flow losses of dense phase flow presents challenges to maintain efficient transfer of the granular material through the branch.
In view of at least the preceding considerations, delivery of granular material by dense phase flow through a branch has many unique challenges that are present in the agricultural industry. Therefore, a need exists for a dense phase branch that overcomes the established challenges.